Multichannel frequency selector and amplifier



July 29, 1952 GARBUNY 2,605,444

MULTICHANNEL. FREQUENCY SELECTOR AND AMPLIFIER Filed Aug. 17, 1948 WITNESSES: INVENTOR z BY Max Garbuny.

l atenteci July 29, 1952 v UNITED, STATES F MULTIGHANNELFREQUENCYfiELECTOfi?" 4 AND AMPLIFIER-i .4 v Maxcarbuny; Pittsburgh, Paglassi'g'iioftbffwe's r iIi'ghouseElec'tric' Corporation; East Pittsburgh, Pal; a corporation-0f Pennsylvania ApplicationiAugust; 17, 194s;;seria11No;;44;e37f

2 Claims? (01. 315:6) 1

M'yinvention relates Itol.anfimproved arrange.-

mentl flfo'r selectively ,amplitying high-frequency alternating voltages, and for-rendering ancillary, electric circuitsaresponsive to any desired oneamong a number of specific frequencies derived from a control circuit. v

Oscillation-generators andamplifiers of ve- 1o'c'ity-.modulated typeknown as the Klystron. are known: in the .art, and these function by projectingna beam ofelectrons ,through a-first alternatingelectric field, then passing them througha substantially field-ireespace for some distance; and then" passingthem through a pontiorif-oflaresonant-chamber or cavity and thencollecting them; on a collecting" electrode positioned beyoncl, the confinesof the latter. In

passing ,throu'gh the first-mentioned alternating.

electric field',l'thei electrons are subjected to a velocity modulation,. retarding 7 them when the alternating fi'eldf is at one polarity andacceleratingf thenionthe subsequent-half cycle when the alternatingvfield is oftheopposite polarity. The.

electrons, accordingly, pass .into the field-free space with differingvelocities which tend to separate them into. a series-of groups .orfbunches moving in spaced relation 'to, eachother, They, V

accordingly, passintoj. the resonant. chamber in this'fb'unchedZ" condition, and it' can be" shown that. thistends' to set the spaceV-with'in the chambe'rlintoi electrical vibration; The'first-mentioned r cavityj resonator. is .refer'redl to as the v buncher andjfrequ'ently takes theform of a pair of spaced grids'fformingn aportion of a resonant chamber Which'is'nsually tuned t0 the same frequency as the," resonant chamber through which the bunched groups p'a'ss".

It-.c'an be" shown vth'at'. thel electrons passing through the field-free space 'first tend to bunch themselves mc'n'ef completely 'as the faster moving.electrons overcome theslower moving electrons; but thi's'bunchi'ng can '.-be' shown to reach a maximum-after a timewhich is a function of the velocity with which the electron, stream is.

projected into the. anernatinewur'rent field and ofgtheiintehsity of that field. i 'However; after, the termination {of the optimum ,bur iching time just'meriuonem it 'cahrbe shown, that the buncha ingl tendencyjceases and iseven'reversed'. The' effectiveness" of the" electron stream in. exciting;

vibrationsv in the resonant-cavityis generally greater 'wnenthebun'chmg' is most complete, and r it willjbe evident, accordingly; that'there is'ia'n;

o timum separationbetween the'l're'son'ant cavjity. and. the alt'ernatingJexciting field which"will gefieratevibrations'in the" resonant" cavitymost' before they pass thronglrthe' resonant cavity.

toe-cause, the elec the; collecting electrode.

effectively. At distances 'either"less"orf greater' than-this optimum separation, the effectiveness" oflthearrangementjis lessened, I V

In? accordance with .thejipresenti mve ec I cause the electron beainlerner'ging from the"'ex'-T citing alternating; new: t'o'ferit'er," no't "lthe new: freeispace ;character istic"of" the prior 1 art, 1 but" a V unidirectional electric 'fie ld, as 1a; resultio'f frwhi'ch the electrons .un'dergo' 'con'tinuousf; acceleratio have discoveredthat .it is possible, by properly' relatinglthel intensity or thelalternating exciting A field o the"ve=-" field-and unidirectioifal fiele'cftr locity. of. the electrons" in the throughout'lthiripasslg in the abQViInrltioned accelerating filizlla.lgroiiiroi 'bunchffoririationtin" which the electronslconst utinglany ionegroup,1 move at equal velocities so that they maintaini thecgroup rormationiunchanged; ,whilefthe distanceabetween any .or'iel'p'air" 'o'ff groups? continu resonant i chamberl, or .-l chamb'ers; w I v relationship" tofeffect this result-will 'be'lde's'c fri 'belowin connection "with the;detailed "descrip tion-of-zthe drawing; sihceit e successivegroup v remainz-substantially intactthroii fidnt their'sub sequentr travel rte:theQcollecitinghnod there 4 longer asingle; optimum. distance by, which excite? into-,ivibrationneed he spaced: ,fi'dlfi ltfie alternatin exciting fieldglhutia series .o'f 'r$0 nant chambers may, if desired; be1locatedfa1o1f the path; traversed by j the groups hefor'e striki V v A. sev'ere.";linii u present in' -thepr-ior art K1fStrOh), to 1ocation f the resonant cavity at a fixed 'di'stancetfrorhf'the'fj exciting field is, .accordingly, .4 obviated bymyiar:

rangement. It 15,; therefore,possib1e to n rfitraveror nietelectrbni' Still another object of my invention is to provide an arrangement by which any one of a plurality of resonant chambers may be excited selectively into vibration by means of a single control voltage of proper frequency.

Still another object of my invention is to provide a relay device by which a plurality of different control circuits may be selectively energized by impressing a proper control frequency on a, novel type of velocity modulated tube.

A still further object of my invention is to provide a novel type of velocity modulated electrical discharge tube in which an alternating control voltage is employed to excite vibrations through the agency of an electron beam in'a resonant circuit.

A still further object of my invention is to pro vide an amplifier'or relay device in which a plurality of control voltages of different frequencies may be caused to separately excite resonant circuits of their respective frequencies with high efficiency. I p r Other objects of my invention are to provide ultra-short Wave amplifiers or relays capable of transmitting'a broad range of different frequencies between their output and input circuits.

Such objectives as I describe have applications in relays and amplifiers useful in multi-telephony, television both ordinary and colon-and in the ultra-high frequency electronic field generall i gther objectsof my invention will become apparent upon reading the following description, taken in connection with the drawing in which thesingle figure isa schematic showing of an electrical discharge tube suitable to embody the principles of my invention for certain purposes.

..Rferring in detail to the drawing, a vacuumtight electrical discharge tube l which may have walls of insulatingmaterial is provided at one end with an electron gun capable of projecting aconcentrated beam of electrons and comprising a: cathode 2, acontrol electrode 3 and an anode 4 of conventional type for this purpose, and supplied from a suitable sourceof direct-current voltage 5 having its'positive terminal grounded. The beam from the electron gun is projected through a pair of aligned-"openings in exciter electrodes 6, I, one of which is supplied with suitable potential from the voltage source 5. 'The exciting electrodes 6, -1 are separated by a dis-' tance corresponding to an electrical transit angle for the crossing electrons of the desired value; thisfmay preferably be 180. The electrodes 6, I also form a portion of an input circuit preferably comprising an exciting coupling 8 which may be connected to an input circuit comprising a concentric line 9, H.

A'fter'passing through the apertures in the exciter electrodes 6, l, the electrons of the beam enter a unidirectional accelerating-field, preferably constant andhomogeneous which is adjusted and maintained by electrodes 1, l2, l3, l'l, I8 and 24. Inside this field. the beam first passes through a pairof aligned apertures in a first pair of work-circuit electrodes l2, l3 which constitute portions of a resonant output chamber'H-l which may be connected to a load through a suitable concentric line or other output transmission circuit 15. After passing through the first workcircuit electrodes I2, l3, the electron beam passes through a similar pair of work-circuit electrodes l1, I8. which are connected to a second resonant output chamber 19 having an output transmission circuit 22. The resonantfrequency of the that at which 1 the last-mentioned electron 4 resonant chamber I9 may be different from that of the resonator M, if so desired.

Any desired number of output circuits similar except for their resonant frequency to the arrangement l2, l3, l4, 16 may be positioned along the path of the electron beam, the dotted portions of the walls of, container l and the arrangement designated by the reference numerals 23 to 25 being intended to indicate such an arrangement. After'passing through some or all of such a series of output chambers, the electron beam passes through an aperture in an electrode 28, which is preferably grounded, and is collected by a suitable electrode 29 on which a voltage source 3! impresses a suitable potential. It will usually be of advantage to make the voltage source 3 i of such polarity that the collector electrode 2a is negative in potential relative to the electrode 28 by an amount sufficient to reduce lcsses and heating of the electrode 29-.

It will be evident from the above arrangement that, if the exciting electrode 1 is made negative to ground, as shown in the drawing, the electrons,

voltages as desired upon the control electrode '3 in a'manner well known in the art. The elec trons thus formed into a beam undergo further acceleration and pass through the space between the exciting electrodes 6, I.

member 8 and the input circuit 9, ll. Ihe electrons in the beam prior topassage through the aperture in electrode 6 will be, on the average, evenly spaced from each other. Let us now consider an electron passing through the field between the exciter electrodes 6, I ate time when the alternating voltage impressed on the electrode l relative'to the electrode 6 is at its negative maximum. For simplicity let us assume the transitangle between 6 and 1 is very small.

The case of larger transit angles does not change the principle discussed. In this latter case, the

field found by the electron at the midpoint of the alternating current field isthen the critical value.

This electron will obviously be slowed down in passing through the field between the electrodes 6 and l and will emerge into the space beyond,

the electrode 1 with a lower velocity than it had in entering the aperture'in electrode 6. On the other hand, an electron which passes through the space between electrodes 6 and I when the alternating voltage impressed therebetween is zero will enter the space beyond electrode 1 at the same velocity it had on passing electrode 6. Similarly, an electron .which enters the space 1 between the electrodes' fi, I when the voltage impressed On electrode 7 relative to electrode Sis at its positive maximum will vundergo an'acceleration and enter the space beyond electrode 7 at a higher velocity than that with which it"entered the aperture in electrode 6.

However, a half period of the alternating-voltage impressed by the input circuit 9, H has in-' tervened between the time that the first mentionedelectron passed through electrode 1 and An alternating con-i trol voltage is impressed on the latter through the I- .y, higher th 11 that at, which it pressed bet vanes or; the electric; field the. firstl The same. consideration peed. tif ac l d at hat ment by and second electron. Inshort, alljilhree velocity at .thetime the ,last -.mentioned 9 lion passes the electrode ,1. I t'.;may-, in fact; Y be shown that most of the electrons entering;

electrodes land 28, they will all. be accelerated e same rate during theiripas'sage between electrodes, and willsubsequently maintain th e nspacings unchanged withintheirgroup.

Inf short, the group traverses the ,space betweenthe electrodes 1 and 28 as a unit; this group is, however, undergoing a continual acceleration to higher velocities as it moves along its path.

After the lapse of a cycle of the voltage impressed on electrodes 6, I by the input circuit 9, I l, the above-described action will be repeated in periodic fashion, with the result that a second bunch of electrons moving as a group with equal velocity will pass through the tube. By the time that happens, however, the first-mentioned group will have traversed a substantial distance along its path and will have been accelerated so that it is moving at a higher velocity than the second. The result of this is that the electron beam is modulated into a series of electron groups or bunches moving along the path toward the aperture in electrode 28 with constantly increasing velocities as they proceed along the path and with the spacing between any two groups continually increasing as time passes while the spacings of the electrons within one group remain essentially frozen.

After passing through the aperture in electrode 28, the electrons are, of course, collected by electrode 29 and returned to the cathode through the voltage supplies 5 and 3|. The example of the three electrons traversing the electrodes 6, I at intervals 90 apart has only 'been cited for convenience of explanation. In

case of sinusoidal alternating voltage, not all the electrons will attain exactly the same speed in the unidirectional field. It is therefore understood thatthe magnitude of the unidirectional field shall be so adjusted to that of the alternating field that optimum bunching is achieved; id est a time-current relation is produced at passage through the output chambers l4, I9, 25, etc., that power transfer to those cavities is a J at see-1 Bt;.'1 re12erl e eti iai e electrodes 1 and 28 to the alt rnating;.voltage .the' unidirectional field, it has the same ,the gthirdflelectron. which; due ,to ,the. nlvelocity 11 enter. the. space. with the .7 rme e l-.- e r u ies i se pel a e made 21 h it jilist cancels tiled crease. obtained inthe ..alter-,.

. ,7 ele" ron'sl. considered; here ,are moving with t the maximuni- ,I have found that: fQI'.;-B.;SiIIUSOidBJHZ'-J alternating;voltagetheibestwbunchingzisr achievedp if electrons, not of i*903 but. of. 1102.7 'elecl.

tricald egrees;, fr,om the zero point of: alternating...

rya l roimiothereroun tit .iscapableof. exciting; suchrenl utnut .ar sonater s I 1 e icie t to vibration regardlessof;-;th e, position -;along the et eb tweene ectrodes. nd 28: at which..the. i rv ao atedl he; m at o menti ne above as characteristic of prior art Klystron be iasmele p muml o i i n: hereethe sq atorr us b -l d 'ete to t ine ie t xiaiiq om; th l elec ron; tream th s .ob: Y

viated inmy arrangement; Consequently, it-isp possible to positionany desired-numberof reso-..

nators atsuccessive points, alongthe path of: the;

electronpath between -electrodes I and ZSrandexcite them I successivelyg into energetic vibration 1 v by a single }ve1ocity,modulated. electron beam he 'f i y w t h h. a l tron?- ere n. xcites. brat s i ga l esonat isra our i. critically dependent uponthe resonant frequency of the latter, and,.is gr eatest, when the latter is equal to thefrequencyof the voltage impressed.,-

by the input circuit 9, [I on theelectrodes 6,, l.. Thus by giving the successivaresonators. I4," I9, etc., different resonance frequencies. and, impressing only one ,o'f ,.these from the -input circuit 9, ll, any desired one of the resonators l'l, I9 and..,.their output. c rcuits. l6, 22.] etc.,,r'nay be.-

efiiciently energized, the other. output. circuits than that one being left undisturbed. My arrangement obviously makes possible a relay or amplifier in which any one of a number of output circuits may be energized selectively and at will by impressing the proper frequency on the input circuit 9, II. This provides an arrangement which is an effective relay for enabling an input circuit to control at will any one of a number of output circuits. Such relays find application in multiplex telephony, television, and the alternating-current technology generally. It will usually be found advantageous to position the resonant chambers of highest frequency most distant from thelexciter electrodes 6 and 1.

However, the use of the above-described arrangement is not confined to employment of a single modulating frequency impressed by'the input circuit 9, ll. Any desired number of the frequencies to which the resonators l4, l9, etc., are tuned may be simultaneously impressed from the input circuit 9, II and the corresponding resonant chambers will all be excited to energetic vibration. By spacing the frequencies impressed by the input circuit 9, ll over a band of any desired width, a similar broad band of frequencies may be excited in an output circuit which is coupled to all of the corresponding resonators l4, 19, etc. The arrangement thus provides a broad band amplifier which may be designed to transmit any predetermined band of frequencies efiiciently. Such broad band amplifiers will find many applications in high frequency alternating-current techniques.

It is, in fact, possible to show that the effectiveness of the bunching action of the electrodes 6 and 1 is so little dependent on the frequency as well as on the distance by which they are separated from the resonant chambers l4, [9, etc.,

in a manner well known in the Klystron art, the

arrangement I have described may be made to act as an oscillation generator capable of operating at any one of the frequencies to which the resonators 14, [9, etc., are designed, or even to generate any plurality of such frequencies simultaneously. V v V While I have described my arrangement as employing electrons to constitute the projected beam, it will be evident that'the above-described principles are applicable to beams comprising any electrified particles. Also while I have described the resonant output chambers as positioned within the region traversed by the unidirectional accelerating field due to electrode 28,

it is within my invention to position any of them in a field-free space beyond that electrode or even in a retarding field such as that in front'of anode 29. It is also evident that, instead of using only I one input coupling, several input couplings or resonators, preferably spaced closely to each other, may be used.

I claim as my invention:

1. An electron discharge device comprising an envelope having therein a source of charged particles and a collecting electrode forming a beam path therebetween, resonant input means along said path for subjecting said particles to an alternating electromagnetic field over af limitedportion of theirpath, means including an electrode in said envelope adjacent said collecting electrode adapted to produce a homogeneous field for accelerating said particles after emerging from said portion of their path, and a plurality of output cavity resonators along said path intermediate said resonant input means and said field producing electrode.

2. An electron discharge device comprising an envelope having therein a source of charged particlesand a collecting electrode forming a beam path therebetween, resonant input means along said pathfor subjecting said particles to an alternating electromagnetic field over a limited portion of their path, means including an electrode in said envelope" between said collecting electrode and said resonant input means adapted to produce a homogeneous field for accelerating said particles after emerging from said portion of their path, and a plurality of output cavity resonators along said path intermediate said resonant input means and said field producing electrode.

MAX GARBUNY.

REFERENCES CITED The following references are of recordin the file of this patent:

UNITED STATES PATENTS Number Name Date 2,280,026 Brown Apr. 14, 1942 2,314,794 Linder Mar. 23, 1943 2,409,608 Anderson Oct. 22, 1946 2,425,748 Llewellyn Aug. 19, 1947' 2,446,572 Bull Aug. 10, 1948 2,494,721 Robertson, Jan. 17, 1950 

